Process of hardening steel poor in carbon.



C. BURIAN. PROCESSO? HARDBNING STEEL POOR IN CARBON APPLIUATION IILED MAR. '7, 1912.

Patented Oct. 29, 1912.

" My invei'ltion relates to articles after being coated with `such .sand contain any organic CMI.: BUE/115th?, 0F BERLIN, GERMANY', ASSIGNOR T0 OFFENE HAINDELSG'EELLSCEMT GEBRDER SCHUBERT, 0F BERLIN, GERMANY.

Losanna.

To all whom fi may concern? Re it known that l", CARL BURIAN, a citizen ot the Empire of Germany, andv residing at Berlin, Germany, have invented. a certain new and useful lniproved Process of Hardening Steel Poor in Carbon, of which the following is a specification.

processes ol hardening steel poor in carbon.

The case-hardening process as employed heretofore consists in packing the objects to be hardened in any desired ceinentation powder and in exposing them ina receptacle, c. g. a sheet-iron box, to the action of the lire.l Non' this case-hardening .process is connected with special ditlicultis when the objects are to be hardened only at predetermined places, and a clear demarcation of the hard and sott parts is necessary.l Here tofore, for attaining this` end, only processes dilicult of execution could be used which,

in spite of their troublesomencss, were by no means reliable vin the results produced.

llcretofore, 'those portions of the articles to be hardened have been covered with a carburr/zing` medium, 'and those portions of the articles'to reinain soft were covered with sand, brick-ddst or the like. ln this connection, the Well'lrnown procedure vof painting apen those portions of the article to be hardened, the medium containing the carbon, by the aid of a binder, or in the form or' a paste, may be used.

According to the present invention, the

the hardening medium are packed in pure burned` silicious sand, and hence in a sand which contains neither calcium nor alumina, nor does constituents owing to the burning burned silicious sand, all injurious influences upon those portions of the articles tobe lrept soft are avoided. Likewise, the layer of hardening' medium coated upon the artcles to be hardened and which coat may be only a few millimeters in thickness, 1s protected from injurious influences.

My process may be carried into practice as follows :-l`he object to be hardened is coated with a known binderor adhesive substance such as glue, molasses, starch, Hour, gumv arabic, fish glue and dextrin mixed with a liquid, iii'hereupon the hardening agent is r applied, by scattering it for example, until sul'licient hardening substance is present.

pecicaton of Letters y.hpplication filed March 7, 19m.

thereof. By using.

PROCESS 0F HARDENING STEEL P091@ :Hit CARBON.

aan ,Patented ossea-mie.. Serial'ffo. 682,10.

The coating is then dried. Those places not to be hardened are then liberated. from the coating by scraping it oii with a knife, file or the like, and it is thus possible to deinarcate exceedingly sharply. In this manner it is possible, for example, to scratch in the ob ject to be hardened a drawing or Aname which is to be excepted from the hardening. My process may be modified by mixing the ordening agent with the adhesive substancel or binder to form a paste which is then applied to the object and subsequently removed in like manner as the hardening agent from the predetermined parts.

` The object is now packed in pure silicions burned sand in a can or similar casing, the

sand being caused to closely surround the object. The can is then subjected in the usual manner to the action of the fire.

One form of apparatus adapted for carry-A ing my process into practice is represented by way of example in vertical longitudinal section in the accompanying drawing.

Referring to the drawing, a designates a box or can and Z1 the parts of the object Whichare to remain soft.

The parts c to be hardened are coated with the hardening agent cl according to my invention. v

' e designates the pure burned sand in which the ob`ect is packed after the application of the ardenlng mass.

f designates a rod which is introduced for determining the hardness.

When carrying my process into practice the box or can a is high y heated. preferably to a bright cherry red, about 850 C., when the applied hardening agent acts. It is preferable to allow the 'object to cool in the box after the termination ofthe hardening operation, then to remove it and to heat itl afresh to a temperature of about 760 C., dark cherry-red, whereupon it is1coolcd in Very cold Water or oil.

It desired, the binder may be applied to only/predetermined parts, that is to say the Whole object'need not be coated With the binder and hardenin agent andthe excess subsequently remove, but a demarcation can be made from the first. In a known process diehard-@ning agent has also been mixed with a binder and applied in the form of dough to the places to be hardened. In this case, however, the heating took place either in a mue or in chambers lled with powdered charcoal. lWhen such a mode of operation is adopted the objects which are not to be hardened are by no ,means protected from the hardening or from other disturbing influences. On the contrary, this is only obtained by'paclring the objects pron f pine, burned, silicious sand, as 1s the case in'my above-described improved process. My-in1 proved process may also be carried into practice as follows 1- Instead of providing.' the parts to be' hardened with a doughy hardening or cementa'gti'on mass and Work-` ing with a'liqud binder, I may surround them with a portable mold, composed of a vided with the 'hardeningl layer The molds i composed of the described fitted as desired.. to the objects, and may have for example the form of a cylinder, tube, dislr, plate or angle.

The use of cernentation or hardening masses composed of pressed carbonifcrous material is known in itself, but no Ventirely satisfactory result can be obtained with these s pressed cementation massesjalone. Only by packing the objects provided with the molds composed of the pressed cementation mass 1n pure burned sand is it possible exactly to demarcate the places or parts of the Inctallic objects which are to be hardened and y hardening or oementation powder, which isV to remain soft, and simultaneously to obadapted to the objects to be hardened andnl tain a certain protect-ion of the places which made by itself, and subsequently hi ess packed in pure, burned, silicious sand.

j The cerncntatin powder can be readily= brought by pressure in suitable matrices, if desired by using a binder, into a rigid mold exactly adapted to the parts or places of the metallic objects to be hardened. The objects can then be litted int-o this mold or the places or parts to be hardened are surround- 'hly heat them according to the above-descri ed proc;

are to remain soft.

I claim The hereindescribed ,process of hardening steel bodies poor in carbon at predetermined places only, which consists in packing the steel body provided at one or more predetermined places' to be hardened with a hardenin mass in pure burned silicious sand, an in subsequently highly heating the packed steel body.

ed with molds adapted -to them. Those In testimony.whcreof,1 affix my signature placesl ot the objects which are not to be After inserting the objects into the mold or after adapting the mold to the places to be hardened the objects are highly heated, as described above",

yhardened are left tree.

packed in pure burned silicious sand.

in. the presence of two witnesses. c

' lCARL BURIAN.

Witnessesi l HENRY HAsPnn,

WOLDEMAR Hanr'r.

pressed cementation-powder mass may beA 

